Escherichia coli is able to utilize the mixture of carbon sources and produce molecular hydrogen (H₂) via formate hydrogen lyase (FHL) complexes. In current work role of transcriptional activator of formate regulon FhlA in generation of fermentation end products and proton motive force, N′N′-dicyclohexylcarbodiimide (DCCD)-sensitive ATPase activity at 20 and 72 hr growth during utilization of mixture of glucose, glycerol, and formate were investigated. It was shown that in fhlA mutant specific growth rate was ~1.5 fold lower compared to wt, while addition of DCCD abolished the growth in fhlA but not in wt. Formate was not utilized in fhlA mutant but wt cells simultaneously utilized formate with glucose. Glycerol utilization started earlier (from 2 hr) in fhlA than in wt. The DCCD-sensitive ATPase activity in wt cells membrane vesicles increased ~2 fold at 72 hr and was decreased 70% in fhlA. Addition of formate in the assays increased proton ATPase activity in wt and mutant strain. FhlA absence mainly affected the ΔpH but not ΔΨ component of Δp in the cells grown at 72 hr but not in 24 hr. The Δp in wt cells decreased from 24 to 72 hr of growth ~40 mV while in fhlA mutant it was stable. Taken together, it is suggested that FhlA regulates the concentration of fermentation end products and via influencing F_OF₁-ATPase activity contributes to the proton motive force generation.

中文翻译：

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大肠杆菌 FhlA 转录激活剂在 pH 7.5 下产生质子动力和 FOF1-ATPase 活性中的作用

大肠杆菌能够利用碳源的混合物并通过甲酸氢裂解酶 (FHL) 复合物产生分子氢 (H _{2 )。}在目前甲酸调节子 FhlA 的转录激活因子在发酵终产物的产生和质子动力中的工作作用中，在利用葡萄糖、甘油混合物的 20 和 72 小时生长时， N'N'-二环己基碳二亚胺 (DCCD) 敏感的 ATP 酶活性，和甲酸盐进行了调查。结果表明，在fhlA突变体中，比生长速率比 wt 低约 1.5 倍，而添加 DCCD 消除了fhlA中的生长，但在 wt 中没有。fhlA中未使用甲酸盐突变但wt细胞同时利用甲酸和葡萄糖。甘油利用在fhlA中比在 wt中更早（从 2 小时开始） 。wt 细胞膜囊泡中 DCCD 敏感的 ATP 酶活性在 72 小时时增加了约 2 倍，在fhlA中降低了 70% 。在测定中添加甲酸盐增加了 wt 和突变菌株中的质子 ATP 酶活性。FhlA 缺失主要影响 72 小时而不是 24 小时生长的细胞中的 ΔpH 而不是 Δp 的 ΔΨ 分量。wt 细胞中的 Δp 从 24 到 72 小时的生长约 40 mV 下降，而在fhlA突变体中它是稳定的。综上所述，表明 FhlA 调节发酵终产物的浓度，并通过影响 F _O F ₁-ATP酶活性有助于质子动力的产生。